Electron discharge device



p 6, 1949- w, c. BROWN 2,480,900

ELECTRON DISCHARGE DEVICE Filed Sept. 3, 1943 2 Sheets-Sheet l AYE/70 mLL/fl/V 6 5/90/4014 Sept. 6, 1949. w. c. BROWN 2,430,900

ELECTRON DISCHARGE DEVICE Filed Sept. 3, 194:5 2 Sheets-Shqet 2 Away/me. W/Lu/m 6. fimmv,

plan Sept. 0, 1949 William C.

Brown, Watcrtown, Masa, aniguor Baytheon Manufacturing Company, Newton, Masa, a corporation of Delaware Application September 3, 1943, Serial No. 501,079

6 Claims. (Cl. 29-25.

This invention relates to a magnetron, and more particularly to a magnetron of the type having a plurality of possible oscillating modes.

Devices of this kind are intended to oscillate in a predetermined primary mode so as to generate a predetermined frequency, and usually comprise a plurality of arms, each pair of which bound a cavity and form an inductance. Each pair of arms also has juxtapositioned surfaces forming a capacitance. Heretofore difficulty has been encountered in that additional modes of oscillation have occurred, as for example, between alternate arms. These additional modes have caused spurious oscillations to be generated, thus consuming energy and reducing the efliciency of the device. It has been found that by connecting alternate arms. the. spurious oscillations are greatly reduced. As heretofore constructed, the means for reducing the spurious oscillations involved certain difficult, as well as expensive, machining operations.

It is a primary object of the invention to provide an improved construction for reducing the tendency for spurious oscillations to occur.

It is a further object of the invention to provide an improved mode of manufacturing and assembling such devices.

The foregoing and other objects of the invention will be made fully apparent to those skilled in the art from a consideration of the following detailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a transverse section taken on the line l-l of Fig. 2 of a magnetron constructed in accordance with my invention;

Fig. 2 is a longitudinal section taken on the line 2-2 of Fig. l;

Fig. 3 is a fragmentary enlarged view of one of the end laminas of the anode structure;

Fig. 4 is a developed section through a coining die and a sheet of material in the process of having grooves coined therein; and

Fig. 5 shows a sheet of material in various stages of the manufacture of a lamina therefrom.

In the embodiment of the invention illustrated 2 that application, alternate laminas are of different diameter leaving projecting heat-radiating fins. The structure built up of the laminas 2 and 3 is provided with end rings 4 and 5providing a space between the end caps 6 and I and the laminate anode structure.

Each of the laminas 2 and 3 has a central opening 8 and slots 9 extending radially from the central opening 8, each of said slots terminatin in a circular opening iii. In this way the anode structure is provided with a plurality of wedgeshaped arms lil8.

When assembled, the openings 8 form a central chamber extending longitudinally throu h the anode structure, which chamber is adapted to accommodate a cathode structure l9. The cathode structure I9 is supported by cathode lead-in conductor rods 20 and 2| which pass through and are sealed in the outer ends of pipes 22 and 23 by glass-seals 24 and 25. The pipes 22 and 23 are also of conductive material, such as copper, and are hermetically sealedin openings in the end rings 4 and 5.

Pole pieces 26 and 21 are positioned adjacent the end caps 6 and 'l to provide a magnetic field directed longitudinally of the. anode structure.

A coupling loop 28, extending into one of the cylindrical chambers provided by the openings [0, has one end thereof fastened to the inner wall of said chamber. The other end of the coupling loop 28 is connected to a lead wire 29 which in the drawings, the magnetron comprises an envelope I forming the anode structure of the magnetron. The envelope l is preferably of highly conductive material, such as copper, and is of a laminate construction being built up of a plurality of laminas 2 and l, as disclosed in the copending application of Percy L. Spencer, Serial No. 436,891, filed March 30, 1942, now Patent No.

2,458,802, dated January 11, 1949. As shown in extends through and is sealed in the outer end of a pipe 30 by a glass seal M. The pipe 30 is also of highly conductive material, such as copper, and hermetically sealed in the side wall of the anode structure.

Devices of this type are intended to operate so that each of the cylindrical chambers formed by the circular openings I0 and its adjacent arms form a circuit tuned to the frequency at which each of the other chambers Ill and its adjacent arms oscillate.

In magnetrons of this type there is a tendency for oscillations to be produced not only in accordance with the above desired mode but also in various undesired spurious modes. One particularly troublesome mode is that in which alternate anode arms form opposite ends of an alternating circuit extending around the back of a.

pair of openings Ill. As more fully described in the copending application of Percy L. Spencer,

Serial No. 421,145, filed December 1, 1941, now

Patent'No. 2,417,789, dated March 18, 1947, this spurious oscillation mode can be substantially eliminated by interconnecting the outer ends of alternate arms' directly by low impedance paths.

Heretofore difllculty has been experienced in makoscillate at the predetermined desired frequency.

By the present invention the above-mentioned difliculties are overcome in the following manner. The outer faces of each of the lamlnas 2 at each end of the anode structure are provided with grooves adjacent the inner ends of the arms |i|8. In alternate arms II, l3. l5 and ll of the top lamina, the groove 32 is relatively shallow and narrow. while in the intervening arms l2, I, II and II. the groove 33' is both wider and deeper than the groove 32. A strap 34 of highly conductive material is secured in the shallow grooves l2-of arms ii, i3, i5 and H by any suitable means, such as soldering or welding,,and passes through the deep grooves 33 without contacting the arms i2, i4, i6 and iii. The strap 34 does not form a closed circuit but is interrupted at ll between adjacent ends of the strap when it is bent into a circle. The interruption 35 is the ring formed by the strap 34 is located at some point between the points of fixation in the shallow grooves 32 and is situated as remote as possible from the coupling loop 28. Thus. as shown, the interruption 35 occurs at one of the deep grooves I2.

In order to avoid the diflicult machine operation which is involved when it is attempted to cut the grooves 82 and I! in the face of the lamina 2, at a point adjacent the ends of the arms il-il, I stamp such grooves in the face of the lamina by a coining operation. Such coining operation would inevitably distort the arms ll-ll, and the ends of the arms I2, I, I and il containing the deeper and wider grooves would be expanded inwardly so that these arms would have a greater length than the intervening arms Ii, I8. I! and i1. Also the end laminas of the laminate anode structure, which are the only ones that are so coined, would have slightly diflerent dimensions than the intervening laminas. Accordingly, in order to avoid all such diiiiculties, I stamp the grooves 32 and 22 in the blank sheet or disk from which the lamina is made before the openings I, the radial slots I. and the circular openings II are punched in the lamina. Accordingly. the precision of the punching operation is in nowise disturbed and as disclosed in the: above-mentioned prior application Serial No. 436,891, the punching operation may be performed so accurately that the lamina may be superimposed to form smooth cylindrical chambers corresponding to the openingssand I, which chambers require no machinins.

The upper portion of Pig. 5 illustrates the first stage in the manufacture of a lamina from which it will be seen that the grooves 32 and 23 are first coined in a blank sheet 31. The coining may be performed in one operation by a coining tool ll, such as shown in the developed sectionandonagreatiyenlargedscaleinl'igi. The tool 88 is provided with dies ll which project ashortdistaneefromthesurfacethereoftocoin grooves 82 in the material 31. The tool is also provided with dies 40 which project for a greater distance than the dies II to coin the grooves 33. It will be understood that the coining of the grooves may be done in more than one operation for convenience. The dies to and 40 may be on separate tools. This portion of the figure is intended to illustrate a stage in the process, rather than a single operation. The grooves 32 and 33 define a circle in which. in one or more subsequent operations. the opening 2 is punched. The openings l0, and the radial slots 9 are also punched in the sheet I! in the positions shown so that the grooves 22 and 32 are thus left adjacent the ends of radially projecting arms iI-i8 in the perforated sheet. The slots 9 are somewhat wider than the space between thegrooves 32 and 33 as shown in the upper portion of Fig. 5, so that in the perforating operation, by which the arms il-II are formed. the slots 32 and 33 will be cleanly cut at the luxtaposed faces of the arms H-il. As shown in the lower portion of Fig. 5, a disk 2 is stamped from the perforated sheet of the material 31 to provide the completed lamina for one of the end lamina of the anode structure. Accordingly, by the present process, the arms |Il8 of the lamina containing the coined grooves 32 and 33 will have the same dimensions as the arms of the other laminas which are not so grooved.

Preferably the exposed face of the lowermost lamina is grooved and strapped by a strap 38 in the same manner as has been described in connection with the top lamina of the stack, except that the arms ll, ll, ii and i1, which were provided with the shallow grooves 32 in the upper lamination, are now provided with the deeper and wider grooves 33 and are not connected to the strap Ii, while intervening arms i2, II, is and I. are provided with the shallow rooves 32 in which the strap 38 is secured, as by soldering or welding. Thus. any arm which is connected to the strap 34 in the upper face of the anode structure is not connected to the strap 36 in the lower face of the anode structure and vice versa.

I have found that the above-described construction substantially eliminates the undesired spurious modes of oscillation without interference with the primary mode of oscillation. Since the coining operation may be performed rapidly upon blank sheets or strips as the same are fed through a stamping machine, the desired results are attained in a manner which is far less expensive than has heretofore been possible. Furthermore, the need for skilled operators and expensive machinery is eliminated.

It will be understood that the invention is not limited to the particular details as described above as many equivalents will suggest themselves to those skilled in the art. For example, the conformation of thecoined slots may vary from the rectangular form shown. The conducting strap need not be circular in cross-section; likewise other shapes or configurations may be used for the anode structure. Various other equivalents within the scope of the appended claims will su gest themselves to those skilled in the art.

What is claimed is:

1. The method of forming strapping grooves in a lamina of an anode structure of the laminate typewhichcom risescoiningaseriesofgrooves inablankshee ofthematerlaiofsaidlamina,

andperforatingsaidsboettolesveproiecting.

acsopoo 2. The method of forming strapping grooves in a lamina of an anode structure of the laminate type which comprises coining a series of alternat-' ing deep and shallow grooves in a blank sheet of the material of said lamina, and perforating said sheet to leave projecting arms having said shallow grooves adjacent the ends of alternate arms and having said deep grooves adjacent the ends of intervening arms.

3. The method of forming strapping grooves in the end face of a perforate anode structure which comprises coining a series of grooves in a body of the material of which said anode structure is to be formed, and perforating said material to leave projecting arms having said srooves adjacent the ends thereof.

4. The method of forming strapping grooves in the end face of a perforate anode structure which comprises coining a series of alternately deep and shallow grooves in a body of the material of which said anode structure is to be forms ed, and perforating said material to leave projecting arms having said grooves adjacent the ends thereof.

5. The method of forming strapping grooves in the end face of a perforate anode structure which comprises coining a series of curved 6 grooves defining a circle in a body of the material of which said anode structure is to be formed, and perforating said material to leave projecting arms having said grooves adjacent the ends thereof.

6. The method of forming strapping grooves in the end face of a perforate anode structure which comprises coining a series of alternately deep and shallow curved grooves defining a circle in a body of the material of which said anode structure is to be formed, and perforating said material to leave projecting arms having said shallow grooves adjacent the ends of alternate arms and having said deep grooves adjacent the end of the intervening arms.

WILLIAM 0. BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

